Disabling the Guest Account
There are a few ways to disable the Guest account – two valid ways and one not so valid way (depending on your Service Pack).
The best way to disable the account is by going through the command prompt.
1) Go to Start, Run and type “cmd". Hit Enter.
2) Type “net user guest". You will see something like that in Figure 1. Note the status under “Account Active" – chances are it’ll say Yes.
3) Type “net user guest/active:no". You should receive confirmation that it worked (Figure 2). Running the “net user guest" command again should show “No" under the “Account active" heading (Figure 2).
Note that some articles out on the Internet tell you that you cannot disable the Guest account using the User Accounts Control Panel. Turning off the user in the User Accounts panel would only disable the ability for the Guest user to log in locally to a machine - the account itself would not be disabled. My guess is that using an earlier version of Windows this statement may have been true, but as of Service Pack 3, going through this method also works.
Note: If you’ve already disabled the account as explained above, there is no need to perform the following procedure.
1) Go to Start, Control Panel, User Accounts
2) Click on the Guest Account (Figure 3)
3) Click “Turn off the guest account". Performing the “net user guest" command as shown in Figure 2, you can see the Account is no longer active.
This is obviously an easier method to follow, but just to be safe, I’d still use the command line route.